Date: Mon, 21 Dec 1998 14:09:59 GMT From: aerodnopsamejanews.com Subject: Re: Ideas Needed: RPM Hunting at Idle
I have an '87 900 and did own an '74 99 both of which will "hunt" at idle if there is any kind of vaccum leak. Just take the oil stick cover off while it is running in the driveway. Hey I should try that on my '94 9000. The check engine light is most likely a sensor. I haven't had to dig into and computer stuff with Saabs yet. I wouldn't know how to get the computer to enter it "diagnostic mode" which would give the code of what sensor was reporting an out of tollerance. On some friends GM cars one could jumper the computer diagnostic port pins 1&2 and get the codes with the key tuned on. As for the frequency numbers 800 RPM (also 800 cycles/min.) would equate to 13.3 cycles/sec (Hz) so at 25 Hz it would be hunting every half revolution, not likely. Just a nit, I work in the frequency domain. Aerod In article <75gi2f$4i9nopsam1.snet.net>, "FRANK VAN HASTE" <frank.vanhastenopsam.net> wrote: > The car in question is a 1989 900, nicely broken in at 104,000 mi. > > When driven energetically then brought down to idle, the RPM will "hunt" > between about 800 and 1400 at maybe 20-25 Hz. Also, on occasion during > extended highway jaunts the "Check Engine" light will come on -- > intermittently at first, then steadily. There is no discernible effect on > performance. > > I am imagining either (a) a failure in the electronic engine control > ("computer") or a problem with a sensor in the engine control system. > > Any ideas on what might be the problem, or how to trouble-shoot, before I > subject myself to the tender mercies of the dealer's service department? > > TIA, > > Frank Van Haste > frank.vanhastenopsam.net > ----- > "Heavier-than-air flying machines are impossible." > > -- Lord Kelvin, President, Royal Society, 1895. > ----- > http://pages.cthome.net/frank.vanhaste > 203-261-8514 > > -----------== Posted via Deja News, The Discussion Network ==---------- http://www.dejanews.com/ Search, Read, Discuss, or Start Your Own
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